active_model_serializers issue undefined method `read_attribute_for_serialization' for {:template_name=>"sample", :template_id=>1, :count=>1}:Hash

[deependersingla]

Hello team,

First off thanks for writing this gem, we use the 0.8.1 version in our app and it works great for us.

This is some strange error which we just start getting on production and will try my best to explain.

Code for one serializer

class Api::V1::OrganizationSerializer < ActiveModel::Serializer
attributes :achievemtents, :templates

def achievements
    object.achievements_summary
  end

  def templates
    object.templates_summary
  end
end

Both method achievements_summary and templates_summary are custom methods which give array of hashes as output.

Output response locally for serializer:

{
     "id": 1,
     "achievements": [{
         "achievement_id": "examplecourse1",
         "count": 4,
         "credential_name": "Example Course"
     }],
     "templates": [{
         "template_name": "sample template",
         "template_id": 3,
         "count": 0
     }]
 }

Now on production we get this error for the same:

undefined method `read_attribute_for_serialization' for {:template_name=>"ftft", :template_id=>1, :count=>1}:Hash
    from /usr/local/share/ruby/gems/2.0/gems/active_model_serializers-0.8.1/lib/active_model/serializer.rb:99:in `block in attribute'

if i comment the second method templates_summary the serializer works fine on production also and give this output:

{
     "id": 1,
     "achievements": [{
         "achievement_id": "examplecourse1",
         "count": 4,
         "credential_name": "Example Course"
     }]
 }

Now few question which I was not able to find answers are:
1) Both on production we uses the same version of serializer 0.8.1 so why this error?
2) In the achievements_custom template also we have a custom array of hashes so why not this error comes on production with that method also?

Ruby version on both: ruby 2.0.0p451 (2014-02-24 revision 45167) [x86_64-linux]
Rails version on both: 4.1.0

I am not really expecting an accurate answer for this, but any good start/advice will also be great for me to put more brain in it.

thanks

[prasadsurase]

Could not reproduce the error with ruby 2.0.0, rails 4.1.0 and active_model_serializers 0.8.1.

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
   source 'https://rubygems.org'

   ruby '2.0.0'

   gem 'rails' , '4.1.0'
   gem 'arel'
   gem 'sqlite3'
   gem 'active_model_serializers', '0.8.1'
   gem 'pry'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

require 'active_record'
require 'active_model_serializers'
require 'minitest/autorun'
require 'logger'

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true  do |t|
    t.string :title
    t.text :body
  end
end

class Post < ActiveRecord::Base
  validates :title, :body, presence: true

  def achievements_summary
    [{ achievement_id: "examplecourse1", count: 4, credential_name: "Example Course" }]
  end

  def templates_summary
    [{ template_name: "sample template", template_id: 3, count: 0 }]
  end
end

class PostSerializer < ActiveModel::Serializer
  attributes :achievements, :templates

  def achievements
    object.achievements_summary
  end

  def templates
    object.templates_summary
  end
end

class BugTest < Minitest::Test
  def test_json
    post = Post.create!(title: 'Test filter', body: 'Test if the filter method is working fine')
    assert_equal PostSerializer.new(post).to_json, {post: {achievements: post.achievements_summary, templates: post.templates_summary}}.to_json
  end
end

[bf4]

My guess it one of the objects doesn't include ActiveModel::Serialization http://api.rubyonrails.org/classes/ActiveModel/Serialization.html

[bf4]

Propose closing as stale. I'm happy to add a test and docs for this scenario if there's a desire.

[joaomdmoura]

@bf4 tests are always welcome! Indeed I'm closing it